From the published patent application DE 2 517 186 A1, a temperature-regulating element is already known for the continuously variable supply or removal of heat by means of a liquid or gaseous heating or cooling medium, with said temperature-regulating element being, in particular, employed in plastics processing. The temperature-regulating element is formed as a hollow tube and separated by a dividing wall into two chambers arranged axially adjacent to one another and connected with a housing. At its free end, the tube is closed with a lid and in this case connected with both axially adjacent chambers by means of a recess so as to ensure circulation or forced reflux of the medium. This construction method obviates the need for elaborately drilled and sealed circulation systems, and the temperature-regulating elements can be employed in an operationally convenient manner and effective position, regardless of the type of tool construction. What needs to be considered in this case, however, is that in this process the entire stretching rod will be temperature-controlled.
The published patent EP 0 511 617 B1 discloses a method involving stretch-blow injection moulding of a hollow body. This method is performed by means of a stretching rod that is formed to be hollow. For this purpose, the temperature of the end portion of the hollowly formed stretching rod is regulated in such a manner as to adjust the temperature to a lower level than that of the preform. As a consequence, the invention supports the direct heat exchange between those parts that are in contact with each other. The heat exchange is achieved by a temperature control medium that circulates through the stretching rod, by said temperature control medium being passed through an inner tube and streaming downward to the end portion of the stretching rod. This medium is subsequently passed back upward through the outer, circular tube. The above method also exposes the entire stretching rod to the process of temperature control. This results in the formation of condensation. Said condensate forms on the preform.